Crank assembly



J. H. WILSON CRANK ASSEMBLY May 5, 1964 3 Sheets-Sheet 1 Original FiledJan. '7, 1955 JohnHari: WllSan INVENTOR.

May 5, 1964 J. H. WILSON 3 ,577

CRANK ASSEMBLY Original Filed Jan. 7, 1955 3 Sheets-Sheet 2 John H artWilson INVENTOR.

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y 1964 J. H. WILSON 3,131,577

CRANK ASSEMBLY Original Filed Jan. 7, 1955 3 Sheets-Sheet 5 47 la 94 90we 86 7a ,6 2a a 2/ Z I J 1 L r36 I I I III! a as t? I 37 I -19 70 a 24ii; 98 o :II ,6 17 19 JohnHart Wilson INVENTOR.

HIS JJGENZ? United States Patent 3,131,577 CRANK ASSEMBLY John HartWiison, Wilson Mfg. Co., R0. Box 1031, Wichita Falls, Tex.

Original application Jan. 7, 1955, Ser. No. 480,445, now Patent No.2,899,742, dated Aug. 18, 1959. Divided and this application Mar. 26,1959, Ser. No. 802,291

2 Claims. (Cl. 74-597) This present application is .a division of myprior application Ser. No. 480,445, filed January 7, r1955 for CrankAssembly, now Patent No. 2,899,742, granted August 18, 1959.

This invention relates to heavy duty pumps and like machinery, andparticularly to a crank assembly suitable for use, for example, in mudpumps such as those used in the drilling of oil wells, where extremelygreat thrust on the piston is required, and where tremendous power mustbe supplied to a relatively small pump.

rVarious types of cranks have been used heretofore, including thatcovered by Patent No. 2,249,802 issued to the present applicant. Thecrank disclosed in this patent comprises a steel casting somewhat in theshape of the letter S and to which a sprocket is attached, and to whichthrow blocks are attached at each end of the center member. This type ofcrank was made and incorporated into a number of pumps, but iscommercially unsatisfactory, since it has been found to be almostimpossible to procure steel castings which are completely free of flaws.

According to the present invention, which has been designed to overcomethe aforesaid difficulty, the sprocket also serves as the centralportion of the crank assembly, and the two crank shafts, which areassembled with the sprocket by means of shrink fits, as well as taperpin keys, constitute a crank assembly far superior to the type mentionedabove.

Various other types of cranks have been used for oil field mud pumps,some of which are made of steel castings or even forgings, and in whichthe connecting rod bearings are made much larger than necessary forintended capacity so as to enable their passage over bent portions oftheshaft.

Shafts of this type are excessively long and they require large andexpensive connecting rod bearings, which, because of their otherrequirements, cannot be of the selfaligning type. Since the shaft will,of necessity, deflect upon the application of a great load thereon,these hearings should be of the self aligning type, but in the case ofthe construction in question, the use of such bearings is practicallyimpossible, both because of the very large size required, and becausenonstandard sizes of bearings are required.

Still other types of pumps make use of an eccentric instead of a crank,but these require verylarge connecting rod hearings, which in turn, arevery expensive and, moreover, are not of the self aligning type. Thistype of construction, therefore is quite large, cumbersome, and costlyto build.

The type of crank embodied in the present invention permits the use ofself aligning bearings, both as main bearings and as connecting rodbearings, and permits the use of a shaft which is shorter and morecompact than is suitable for use with any construction employedheretofore. Therefore, there is less bending strain on the shaft, andthe hearings can be removed for replacement, should they become worn ordamaged in service.

The crank shaft embodied in the present invention is assembled ofseveral component parts, and thus the metal in a particular part,preferably a forging, can be of the proper alloy and strength so thatthe unit, when assembled, gives the maximum performance with the minimumcost, and should any imperfections occur in a particular part,

Patented May 5, 1964 that one part only can be discarded without thenecessity of discarding the entire assembly. The relatively shortstraight shaft of the present invention can easily be tested for flawsand defects by high-frequency-sound testing devices.

It has been found that the crank pins, when made of the same material asthe rest of the crank assembly, will break before any other portion ofthe crank assembly. With the present arrangement, the crank pins can bemade of a more suitable type of metal and alloy so as to make themstronger, so they will not have to be replaced.

An object of this invention is to provide :a crank shaft unit, whereinthe several component parts are assembled securely together to form acrank shaft for pumps, such as mud pumps and the like, engines or othermachinery.

Another object of this invention is to provide a crank shaft assemblywherein the crank pins consist of independent lengths of shaft, on whichthe crank arms and the intermediate portion of the crank are securedtogether so as to present -a crank shaft that may be assembled about abearing.

Yet another object of this invention is to provide a crank unit whichmay be disassembled and reassembled to en able the replacement or repairof the parts thereof, and particularly the bearings employed therewith.

Still another object of this invention is to provide a crank shaft thatis so constructed that the various parts may be assembled together on aline-up bar and a drilling operation performed thereon, which willenable reassembly after disassembly, without using a line-up bar.

A still further object of the invention is to provide a crank shaftassembly wherein the removable portions on the end can be perfectlyaligned so that the crank sprocket will run true when the assembly turnson the main bearings, and also so that the crank pins can be removed forreplacement of the bearings, and when reinstalled on the center portionof the crank, will align so that the sprocket will run true and thecranks will be in proper relation.

With these objects in mind and others which will become manifest as thedescripition proceeds, reference is to be had to the accompanyingdrawings in which like reference characters designate like parts in theseveral views thereof, in which:

FIG. 1 is an exploded view of the crank shaft assembly and showing analigned shaft in dot-dash outline therethrough;

FIG. 2 is a fragmentary elevational view of a pump with parts brokenaway and with parts shown in section to show the details of constructionof the crank shaft therein;

FIG. 3 is a sectional view taken on the line 3--3 of FIG. 2, looking inthe direction indicated by the arrows;

FIG. 4 is a fragmentary detail view showing the manner in which thecrank throws are secured to the crank shaft by means of taper pins;

FIG. 5 is a perspective view of a spacer ring element; and

FIG. 6 is an elevational view of a crank shown apart from the crankshaft.

With more detailed reference to the drawing, the numeral ll designatesthe crank case housing of a pump, in which a crank member, generallydesignated at 14, is journaled in bearings 16, mounted within bearinghousings 18 which are removably secured to the housing 11 by means ofcap screws 22. The bearing housing 18 is sup ported in the housing 11 bymeans of the tapered wedge blocks 19 which are pulled into place bymeans of cap screws 21. These Wedge blocks seat against the taperedsurface 17 and take up all the play between the bearing housing and theframe. And if, due to Wear, play should become apparent, the wedgemembers can again be taken up by means of the cap screws 21.

The crank unit, which is generally designated by the numeral 14, isassembled from several component parts, as will be fully brought out asthe description proceeds. As seen in FIG. 1, a sprocket 24 has a hub 26through which an axial opening 28 is formed. The hub 26 has bores 30 and32 (FIG. 3) therethrough, which bores are in parallel relation with theaxial bore 28. The respective bores 30 and 32 receive members 34 and 36respectively, from opposite sides of the hub 26, which members projectoutwardly of the hub to form crankpins, as will be seen from FIG. 1.Crank arms 38 and 40 have bores 42 and 44, respectively, which bores areof a size to receive crankpins 34 and 36, respectively, when the crankarms are properly expanded, as will be fully brought out hereinafter.

The crank arms 38 and 40 have bores 46 and 48, respectively, which boreswill align with the axial bore 28, when the crank arms 38 and 40 areproperly fitted on crankpins 34 and 36. When the crank arms 38 and 40are in place, holes are drilled in the end of the crankpins 34 and 36and crank arms 38 and 40 are reamed so as to be tapered, so thatapproximately one-half the hole, as indicated at 50, is in the crankarm, and the other half in the hole, as indicated at 52, is in the pin,so as to receive tapered pins 54, which hole and pin arrangement forms akey to prevent rotation of the crank arms 38 and 40 with respect tocrankpins 34 and 36. The outer ends of the respective crankpins 34 and36 are drilled and tapped, as indicated at 56, to receive cap screws 58,which are adapted to secure plate 60 to the ends of the shafts toprevent outward movement of the respective crank arms 38 and 40.

Bushings 62 and 64, which have cylindrical outer surfaces, are provided,which bushings are adapted to fit within the axial bore 28, and whichbushings each have a bore therein of substantially the same diameter asthat of the line-up bar 66. Bushings 63 and 65, the bores of which fitsnugly on line-up bar 66, have their inner ends tapered so as tointerengage the outer edge of the counterbores 47 and 49, respectively,when the crank shaft is being heated, expanded and assembled. When thebushings 62 and 64 are in axial bore 28 and the bores 46 and 48, of therespective crank arms 38 and 40, are aligned by tapered bushings 63 and65 being fitted within the respective counterbores 47 and 49, the crankarms 38 and 40 on the respective crankpins 34 and 36 are aligned withrespect to rotation, so that the sprocket 24 will run true with therotational axis of outer bearing portions 82 and 84, as will be morefully explained hereinafter.

In the completed assembly of the crank arms 38 and 40, respectively,they are spaced away from the respective hub bosses 68 and 70 by therespective spacer rings 73 to accommodate anti-friction connecting rodbearings 72 for the connecting rods 74. Thus it is possible to useantifriction bearings of the self-aligning type, and also bearings whichare not split, as the anti-friction bearings 72 may be fitted onto therespective pins 34 and 36 before the arms 38 and 46 are placed inposition on the respective crankpins. Plates 78 and 80 are secured tothe outer bearing portions 82 and 84 of the respective arms by means ofcap screws 86 and 88, respectively, which plates hold the bearings 16 inplace. Bearing cover plates 98 and 92, respectively, are secured to thehousing 11, as will be seen from FIG. 3, by means of cap screws 94 and96, respectively.

In the completed assembly, the bores 46 and 48 of the crank arms 38 and46 are plugged by means of plug members 98 and 183. Each of the plugs 98has a lubricant fitting 102 therein so lubricant can be forced throughthe respective bores 46 and 48 and through branch passages 184 and 106,which passages will be lubricated while the pump or the like is inoperation.

ASSEMBLY In the fabrication of the crank unit, the bores 38 and 32,within hub 26, are made slightly less in diameter than the respectivepins 34 and 36. In assembling the unit the sprocket 24 and hub 26 areheated so that the respective bores 30 and 32 will expand sufficientlyto permit the respective pins 34 and 36 to be inserted thereinto. Whenthe pins are fitted in place and the hub has been allowed to cool, holesare drilled, which holes are drilled so that approximately half of eachhole is in the hub and half in the respective pin. The holes are thenreamed and tapered pins 37 are inserted thereinto, substantially asshown in FIG. 3, and as shown in FIG. 4.

With the pins 34 and 36 thus positioned within the hub 26, and keyed inplace by means of tapered pins 37, the sprocket 24 and hub 26, which arenow cool, will have a secure gripping action on the respective pins.

After this step of the assembly has been performed, spacer rings 73(FIG. 5), of the same length as the bearing races 72, are telescopedover the respective pins 34 and 36, so as to shoulder against therespective bosses 68 and 78. The crank arms 38 and 40, which have therespective bores 42 and 44 therein, which bores are slightly smallerthan the respective pins 34 and 36, are heated until the arms expandsufficiently to allow the respective bores 42 and 44 to be telescopedover the respective pins 34 and 36, and with the bushings 62 and 64 inplace Within axial bore 28, and with the shaft 66 fitted within thebushings, the arms 38 and 40 have their respective bores 46 and 48telescoped over shaft 66 until the bores 42 and 44 telescope over therespective pins 34 and 36 against spacer rings 7 3, and with therespective arms in tight fitting relation with the spacer rings 73, withline-up bar 66 in place, tapered line-up bushings 63 and 65 are fittedsnugly into counterbores 47 and 49, then the arms are allowed to cool,however, the tapered bushings 63 and 65 are moved axially outward as thecooling progresses to compensate for the size of the counterbores 47 and49, thereby enabling an accurate fit to be maintained. Threaded plugs98, having a center in the outer end, are then screwed into the outerends of cranks 38 and 40. The whole crank unit is then put on centers,as in a lathe, and tested to see if it runs true. Holes 58 and 52 arethen drilled so as to intersect the mms and the respective shafts, whichholes are reamed to receive tapered pins 54. Approximately half of eachhole, as indicated at 50, is within the crank arm, and the other halfthereof, as indicated at 52, is within the shaft. Tapered pins 54 aredriven into the holes thus formed, thereby assuring the respective crankarms are secured in proper fixed relation to the respective shafts. Thetapered pins 54 are then removed, by screwing a threaded rod in a holein the end of the taper pin, and the pins 34 and 36 are thus pressed outof the respective crank arms 38 and 40. The spacer rings 73 are thenremoved from the respective pins 34 and 36 and bearings 72 aresubstituted for the spacer rings 73, and with the connecting rods inplace on the bearings, the crank arms 38 and 40 are heated so as toexpand the bores 42 and 44 thereof to enable the crank arms to beinserted onto the respective crankpins 34 and 36 to the exact place andin the same relation as the crank arms previously occupied on therespective crankpins. Whereupon, the tapered pins 54 are reinserted intothe reamed, tapered holes formed by the complementary grooved portions50 and 52. With the tapered pins in place, the plates 60 may be boltedin place on the ends of the respective crankpins by means of cap screws58, so as to hold the tapered pins and the crankpins againstlongitudinal movement. After the crank shaft has been assembled in thismanner, it may be fitted within housing 11, in its main bearings 16.

It is to be pointed out that the respective crankpins 34 and 36 may bemade of high strength forged alloy steel or the like, was to withstandthe hardest usage, and may be easily and effectively tested, and yet thesprockets and crank arms may be made of suitable material, therebygreatly reducing the size of the respective crankpins 34 and 36, but atthe same time providing a unit which is much more likely to be free offlaws and imperfections,

than would a crank shaft assembly that is cast as an integral unit.

It is to be further pointed out that, by the use of removable taperedpins 37 and 54, the respective crank pins and bearings may be removedand replaced, if they become worn, or various elements of the assembly,such as the arms or the sprockets, may be replaced without having toreplace the entire assembly, thereby making possible a materialreduction in the cost of producing and maintaining such units.

While the invention has been described and illustrated in some detailfor use with pumps, it is to be pointed out that this arrangement may beapplied to the assembly of other machinery using cranks of thischaracter, such as engines and the like.

Having thus clearly shown and described the invention what is claimed asnew and desired to secure by Letters Patent is:

1. A crank shaft for a reciprocating pump comprising a hub member havingtwo holes extending therethrough parallel to the rotational axis thereofand spaced from said axis, a sprocket integrally formed with said hubmember, shafts secured in said holes and extending outwardly from saidhub member in opposite directions, with the respective axes of saidshafts in parallel relation with the rotational axis of said hub, acrank member attachably secured to each of said shafts at a spaceddistance outwardly from said hub, a second series of shafts, each ofsaid last-mentioned shafts being integrally formed on one of said crankmembers and extending outwardly therefrom with its axis in parallelrelation with the axes of said first-mentioned shafts, said sprocketforming power transmission means for said crank shaft.

2. A crank shaft for a heavy duty reciprocating pump comprising a hubmember, having two holes, extending therethrough parallel to therotational axis thereof and spaced substantially degrees apart andspaced from said rotational axis thereof, a drive sprocket integrallyand externally formed with said hub member, pins shrink fitted and keyedto said hub, in said holes and extending outwardly from said hub memberin opposite directions, with the respective axes of said pins inparallel relation with the rotational axis of said hub, a crank memberattachably secured to each of said pins at a spaced distance outwardlyfrom said hub, a pair of shafts, each of said shafts being integrallyformed on one of said crank members and extending outwardly therefromwith its axis in parallel relation with the axes of said pins and saidsprocket and said crank members being securely fitted on and pinned tosaid crank pins.

References Cited in the file of this patent UNITED STATES PATENTS393,211 Ohase et a1 Nov. 20, 1888 1,347,178 Schenk July 20, 19201,485,645 Tindale Mar. 4, 1924 1,552,746 Kizer Sept. 8, 1925 1,567,986Ricardo Dec. 29, 1925 1,652,617 Eurit Dec. 13, 1927 1,705,375 RichardoMar. 12, 1929 2,249,802 Wilson July 22, 1941 2,364,109 Taylor Dec. 5,1944 2,380,099 Dusevoir July 10, 1945 2,475,011 Chilton July 5, 19492,643,145 Sundbom et a1. June 23, 1953 2,730,912 Marinelli Jan. 17, 19562,899,742 Wilson Aug. 18, 1959 FOREIGN PATENTS 645,233 France June 26,1928

1. A CRANK SHAFT FOR A RECIPROCATING PUMP COMPRISING A HUB MEMBER HAVINGTWO HOLES EXTENDING THERETHROUGH PARALLEL TO THE ROTATIONAL AXIS THEREOFAND SPACED FROM SAID AXIS, A SPROCKET INTEGRALLY FORMED WITH SAID HUBMEMBER, SHAFTS SECURED IN SAID HOLES AND EXTENDING OUTWARDLY FROM SAIDHUB MEMBER IN OPPOSITE DIRECTIONS, WITH THE RESPECTIVE AXES OF SAIDSHAFTS IN PARALLEL RELATION WITH THE ROTATIONAL AXIS OF SAID HUB, ACRANK MEMBER ATTACHABLY SECURED TO EACH OF SAID SHAFTS AT A SPACEDDISTANCE OUTWARDLY FROM SAID HUB, A SECOND SERIES OF SHAFTS, EACH OFSAID LAST-MENTIONED SHAFTS BEING INTEGRALLY FORMED ON ONE OF SAID CRANKMEMBERS AND EXTENDING OUTWARDLY THEREFROM WITH ITS AXIS IN PARALLELRELATION WITH THE AXES OF SAID FIRST-MENTIONED SHAFTS, SAID SPROCKETFORMING POWER TRANSMISSION MEANS FOR SAID CRANK SHAFT.